1. Field of the Invention
The present invention relates to a cutting tool comprising a head segment and a shank segment, especially a cutting tool has a feature that the head segment releasable from the shank segment.
2. Related Art
FIGS. 25 and 26 show a conventional cutting tool which has a generally cylindrical cutting tool body 10 having a shank segment 11 and a head segment 12. The shank segment 11 is adapted to be fixedly secured to a machine spindle (not shown) so that the cutting tool body 10 can be rotated about an axis passing thereof. The shank segment 11 is made of a high-rigid material such as a cemented carbide alloy which can be used for preventing deflection or chatter vibration of the body 10.
The head segment 12 has a generally hemispherical forward end and a rearward end and is made of an easy-processing material such as a steel. In general, at least one insert receiving recess is formed in the forward end of the head segment 12, in which a cutting insert 3 is fixed by a clamp screw 4, while the reward end of the head segment 12 is joined with the shank segment 11 at a joint portion 13 by means of brazing.
However, the conventional cutting tool described above has some problems:
(i) it is difficult to detach the head segment from the shank segment because they are joined each other by the braze as mentioned above, so that the head segment can hardly be exchanged for another one when the head segment is damaged or when a different type of the head segment is required;
(ii) it is also difficult to bring the end face of the head segment in contact with the end face of the shaft segment with a required accuracy, so that the head segment and/or shank segments requires at least one positioning marker or positioning mechanisms.
FIG. 27 shows another type of a conventional cutting tool which is fabricated for solving the above problem (i). As shown in the figure, an external thread 17 is coaxially provided with the shank segment 14, while an internal thread (not shown) is coaxially formed on the head segment 15. Consequently, these segments 14 and 15 are joined by threads so that the head segment can be easily replaced with another one.
In this case, however, the internal and external threads have their own tolerances so that it is difficult to adjust the relative position between the head 15 and the shank 14 in a circumferential direction. For example, it is difficult to adjust the relative circumferential position between a cutting insert 3 and a chamfered corner 16 of the shank 14 when the head 15 and the shank 14 are tightened with the external thread 17. Accordingly, the above described joining means cannot be used for the work rotating cutting method but can be used for the tool-rotating cutting method.
Furthermore, it is difficult to fabricate the external thread in a unitary construction with the shank when the shank is made of a cemented carbide alloy. In addition, in the case that an external thread segment is manufactured from an easy-processing material such as steels and joined with the shank segment by means of brazing, additional processing steps or the like would be required, resulting in the complicated fabricating process of the cutting tool.